Re: [RFC PATCH v2 1/3] sched, tracing: add to report task state in symbolic chars

[Peter Zijlstra]

On Wed, Jul 26, 2023 at 08:16:16PM +0800, Ze Gao wrote:
> Internal representations of task state are likely to be changed or
> ordered, and reporting them to userspace without exporting them as
> part of API is not a good choice, which can easily break a userspace
> observability tool as kernel evolves. For example, perf suffers from
> this and still reports wrong states by this patch.
> 
> OTOH, some masqueraded state like TASK_REPORT_IDLE and TASK_REPORT_MAX
> are also reported inadvertently, which confuses things even more.
> 
> So add a new variable in company with the old raw value to report task
> state in symbolic char, which is self-explaining and no further
> translation is needed, and also report priorities in 'short' to save
> some buffer space.  Of course this does not break any userspace tool.
> 
> Note for PREEMPT_ACTIVE, we introduce 'p' to report it and use the old
> conventions for the rest.

So I really dont much like this. This looses the ability to see the
actual wait state flags, there could be multiple. Eg, things like
TASK_FREEZEABLE gets lost completely.

And this is on top of my reluctance to touch any of this at all, for
fear of further regressions.